The invention relates to clamping and gripping devices and, more particularly, to a mechanism for clamping a workpiece and lifting the workpiece from a work surface during a manufacturing operation.
One type of conventional assembly for clamping a workpiece and lifting the workpiece from a work surface includes a clamping mechanism and a separate lifting mechanism. The clamping mechanism generally includes a pair of clamp arms pivotally supported by a frame. Each clamp arm has an end for engaging the workpiece and is supported by the frame for pivotal movement about a pivot axis. A drive mechanism, such as a pneumatically driven piston, is operatively connected to the clamp arms through a link assembly to cause pivotal movement of the clamp arms between a clamped position, in which the clamp arms clampingly engage the workpiece, and an unclamped position.
The separate lifting mechanism is provided to lift the clamping mechanism while the workpiece is clamped. The workpiece is thereby lifted from the work surface so that, for example, the workpiece can be moved to another work surface. The lifting mechanism is generally operable between a lifted position and a non-lifted position.
One independent problem with the above-described conventional clamping and lifting assembly is that the assembly includes a clamping mechanism and a separate lifting mechanism. As a result, the assembly requires separate components for the clamping mechanism and for the lifting mechanism. This increases the cost and complexity of the conventional clamping and lifting assembly.
Another independent problem with the conventional assembly is that separate controls are required for the clamping mechanism and for the lifting mechanism. This increases the complexity of the control system for the assembly.
Yet another independent problem with the conventional assembly is that, because separate controls are provided for the clamping mechanism and the separate lifting mechanism, the control for the clamping mechanism may be accidentally operated so that the clamping mechanism moves to the unclamped condition while the lifting mechanism is still in the lifted condition, causing the lifted workpiece to be dropped.
A further independent problem with the conventional assembly is that, if fluid pressure is lost while the workpiece is clamped and lifted, the lifting mechanism may move to the unlifted condition and/or the clamping mechanism may move to the unclamped condition, causing the workpiece to be dropped.
The present invention provides an improved clamping and lifting mechanism that substantially alleviates one or more of the above-described and other problems of conventional clamping and lifting assemblies. The present invention provides a clamp combining clamping and lifting of a workpiece in a single mechanism. The clamping and the lifting of the workpiece are controlled by a single control assembly. This provides a simpler and less expensive mechanism.
Also, the present invention provides a clamp in which the workpiece cannot be accidentally unclamped while in a lifted position. Further, when the workpiece is clamped and lifted, the clamp is mechanically locked in this condition so that a loss of fluid pressure will not result in the workpiece being dropped and/or unclamped.
The present invention provides a clamp for clampingly engaging a portion of a workpiece and for lifting the workpiece from a work surface. The clamp comprises a frame assembly defining a longitudinal axis, an actuating assembly supported by the frame assembly and including a movable member, the actuating assembly preferably being a fluid actuated piston and cylinder assembly including a reciprocating piston having a projecting end movable between a retracted position and an extended position, and at least one clamp arm and, preferably, first and second clamp arms supported by the frame assembly for pivotal movement about respective first and second pivot axes and for axial movement relative to the frame assembly along the longitudinal axis, the first and second clamp arms being connected to the piston. Movement of the projecting end from the extended position to an intermediate position causes pivotal movement of the clamp arms to a clamped position, in which the workpiece is clampingly engaged by the clamp arms. Further movement of the projecting end from the intermediate position to the retracted position causes axial movement of the clamp arms to the clamped and lifted position.
Preferably, the first and second pivot axes are axially moved relative to the frame assembly as the clamp arms are moved from the clamped position to the clamped and lifted position. The clamp preferably further comprises first and second pivot pins respectively defining the first and second pivot axes, and the pivot pins are axially moved relative to the frame assembly as the clamp arms are moved from the clamped position to the clamped and lifted position.
Preferably, the frame assembly defines axially extending first and second tracks, and the first and second pivot pins are respectively supported in the first and second tracks for axial movement along the tracks relative to the frame assembly. The clamp may further comprise first and second slider members respectively supported in the first and second tracks for axial movement along the tracks relative to the frame assembly, and the first and second slide members respectively support the first and second pivot pins so that the pivot pins are axially movable relative to the frame assembly.
The clamp preferably further comprises first and second link pins supported proximate the opposite ends of the first and second clamp arms, respectively, and first and second link members connecting the first and second link pins, respectively, to the projecting end such that movement of the projecting end between the extended position and the retracted position causes movement of the clamp arms between the unclamped position and the clamped and lifted position.
The clamp may further preferably comprise first and second track follower pins supported by the first and second clamp arms, respectively. When the clamp arms are in the unclamped position, the first track follower pin is positioned in a first arcuate track and the second track follower pin is positioned in a second arcuate track. As the clamp arms move from the unclamped position to the clamped position, the first track follower pin moves along the first arcuate track and the second track follower pin moves along the second arcuate track. As the clamp arms move from the clamped position to the clamped and lifted position, the first track follower pin moves along the first track and the second track follower pin moves along the second track, and as the first and second track follower pins move along the first and second tracks, respectively, the clamp arms are prevented from moving to the unclamped position.
Also, as the first track follower pin moves from the first arcuate track to the first track, a portion of the first track follower pin preferably moves into the first cam portion. Similarly, as the second track follower pin moves from the second arcuate track to the second track, a portion of the second track follower pin preferably moves into the second cam portion. When the clamp arms move from the clamped position to the clamped and lifted position, the first and second cam portions are substantially misaligned with the first and second arcuate tracks, respectively, such that the clamp arms are prevented from moving to an unclamped position.
Preferably, the slider members are supported with play in the first and second tracks, respectively, and, when the clamp arms are in the clamped and lifted position, a clamping force applied by the clamp arms causes the first and second slider members to pivot about the first and second link pins, respectively, to become wedged in the first and second track, respectively.
The clamp may further comprise a lift member supported by the projecting end and having a surface engageable with the first and second link members. When the clamp arms are moved to the clamped and lifted position, the surface engages the first and second link members to move the link members to an over-center position.
In addition, the clamp may comprise first and second track followers respectively supported by the first and second link pins, the first track follower being movable along the first arcuate track and the first track, and the second track follower being movable along the second arcuate track and the second track. Also, the clamp may comprise a piston link pin supported by the projecting end and connecting the piston to the first and second link members, and a roller supported by the piston link pin and movable along the center track.
Further, the clamp may comprise first and second workpiece retaining spring assemblies supported in the workpiece engaging end of the first and second clamp arms, respectively.
One independent advantage of the present invention is that a single mechanism is capable of both clamping a workpiece and then lifting the workpiece from a work surface, reducing the cost and complexity of the mechanism.
Another independent advantage of the present invention that the first and second clamp arms are moveable between an unclamped position and a clamped and lifted position relative to the frame by a single piston cylinder assembly, rather than having a separate assembly to lift the clamping mechanism. Also, only a single control is required to control both the clamping and the lifting of the workpiece. This also reduces the cost and complexity of the mechanism and the control for the mechanism.
Yet another independent advantage of the present invention is that, by positioning of the link pins in the axially extending tracks while the clamp arms are moved from the clamped position to the clamped and lifted position, the clamp arms are prevented from moving to the unclamped position as the workpiece is lifted.
A further independent advantage of the present invention is that, when the workpiece is in the clamped and lifted position, the clamp is mechanically locked in this condition so that a loss of fluid pressure does not result in the workpiece being dropped and/or unclamped.
Other independent features and independent advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.